Variable length beam

ABSTRACT

A beam comprised of sub-components capable of extending or contracting in overall length is provided. The beam consists of a twin-beam structure that provides travel support for two end beam components that are movable with respect to one another to extend or contract the length of the resulting variable length beam. Extension or contraction of the variable length beam can be accomplished manually or, in a preferred embodiment, by means of a screw drive. The variable length beams facilitate the fabrication of reusable, adjustable width deck-forming panels used in the construction of cast-in-place bridge deck slabs supported by parallel structural beams.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to bridge building. In one of its more particularaspects it relates to a variable length beam which is useful forfabricating reusable, adjustable width deck-forming panels used toconstruct cast-in-place concrete bridge deck slabs supported by parallelstructural beams.

2. Description of the Related Art

Bridges provide grade separation to facilitate the efficient transportof vehicles, pedestrians and rail systems over roads, railways, chasms,water, and other obstructions.

A typical bridge consists of a series of foundation substructures totransfer loads into the earth, and a superstructure to transfer loads tothe substructure. The majority of bridges built use a system of parallelbeams, either pre-cast concrete or steel, to span the distance betweenfoundation elements. Typically, the system of parallel beams will bebraced at regular intervals and normal to their centerlines by ahorizontal structural member referred to as a “diaphragm”. The spacebetween these parallel beams is commonly referred to as a “bay”, thewidth of which is typically between 4 and 12 feet. The superstructuresurface, which carries traffic loads, is provided by forming a steelreinforced concrete bridge deck, which is formed and cast in place overthe bridge beams.

The cast-in-place bridge deck must be temporarily supported by a systemof falsework that is usually suspended from the structural beams. Alarge variety of systems exist in the marketplace that employ hangerassemblies or threaded rod to hang vertically, or near vertically, fromthe structural beams, which are in turn used to support transverse joistmembers that will ultimately transfer the deck dead load to thestructural beams by supporting a plywood surface onto which thecast-in-place concrete is poured.

The entire temporary falsework system can be adjusted vertically toaccount for beam deflections caused by the weight of the concrete andreinforcing steel.

The spacing and size of the temporary transverse joist beams vary,dependent upon the spacing between the parallel bridge beams and theload that needs to be supported. A reusable temporary deck formingfalsework system needs to be able to be adjusted to variable bay widthsfor different bridges.

Once the cast-in-place concrete deck has been poured and cured, thetemporary falsework system must be stripped from beneath the finisheddeck.

Numerous methods of constructing the falsework decking system exist inthe marketplace today. Concrete forming systems comprised of steelcomponent pieces used to carry construction loads are commerciallyavailable in the world-wide marketplace. These component pieces aremanufactured in a wide variety of sizes and shapes, and can be combinedinto myriad configurations, much like a large “Erector set”, in order tosupport horizontal and vertical loading conditions. Using these membersin a horizontal capacity to function as transverse joist members is astandard practice in cast-in-place bridge deck forming. However, nocomponent piece that will allow transverse joist members to beconfigured into a continuously variable length has yet been provided.

SUMMARY OF THE INVENTION

A transverse joist member designed to provide a continuously variablelength would revolutionize the forming and stripping of the temporaryfalsework, allowing it to be fabricated off-site in modular panels, hungin place as a complete unit, designed to fit between structural beamdiaphragms, adjusted to elevation, and stripped as a complete unit fromthe underside of the finished deck. Only slight modifications to thepanels will be necessary, by removing a small portion of the plywoodsheet and adjusting the continuously variable length transverse joistmember to establish the new joist length. Adding or subtracting stringerbeams as needed and replacing the portion of plywood sheet needed tofill in the panel will yield a system ready for the next use. In someinstances it may be necessary to add or subtract a combination of fixedbeam components to develop a new joist length.

The present invention provides a variable length beam, which can be usedin combination with a fixed length support beam to continuously adjustthe length of the combination. Since support beams typically comprise acombination of fixed length beam components (1′-6″, 3′-0″, 6′-0″, and12′-0″ beam components), attaching a beam component which iscontinuously adjustable in length will enable the resulting combinationto be used across the full range of bridge deck bay widths seen in theheavy highway construction industry throughout the world today. Thevariable length beam component will allow deck formwork joist beams, forexample, to be adjusted to the precise width required to fit betweenbridge beams.

The present invention comprises a uniquely fabricated twin-beamstructure that acts as a travel support to two slightly modifiedpre-existing end beam components, typically two 1′-6″ beam components,that are movable with respect to one another to extend or contract thelength of the twin-beam structure. The two pre-existing beam components,which are currently available in the marketplace, each has a pair ofoppositely facing side channels. They are modified by replacing one oftwo pre-existing end-plates on each end beam component with a platewelded between the oppositely facing side channels. Stop tabs areprovided at each end of the two travel support beams. Two side platesare added to the outside flanges of each of the pre-existing beamcomponents to stiffen the members for load transfer and to serve aspredetermined stop sites for the stop tabs on the ends of the travelsupport beams. The modified members, referred to above, reside atopposite ends of the variable length beams. The twin travel supportbeams are connected with a central stiffener assembly and are fabricatedto move within the cross-section of the end beam components. Alignedslots and holes in the top and bottom flanges of the end beam componentsand the travel support beams are used for placement of structural boltsthat lock the variable length beam into its required length. The overalllength of the variable length beam can be adjusted by manually slidingthe two end beam components along the travel support beams.

In a preferred embodiment of the present invention the two end beamcomponents are moved by a horizontal screw drive with screw drivereceiving plates welded between their oppositely facing side channels atone end in lieu of the standard end-plates. One screw drive receivingplate is a clockwise-threaded plate and the other is acounterclockwise-threaded plate. Side plates are added to the sidechannels to stiffen the components for load transfer and to serve aspredetermined stop sites for the stop tabs on the ends of the travelsupport beams. One end of the screw drive, referred to herein as theproximal end, has a clockwise or standard thread. The other end,referred to herein as the distal end, has a counterclockwise or reversethread. The screw drive also acts as a structural component to provideload transfer to the twin travel support beams. The screw drive has acentrally located bevel gear affixed to its horizontal shaft that isdriven by a smaller bevel gear on a vertical shaft that is aligned to ittangentially and kept in a fixed alignment by keeper plates on the screwdrive shaft. A user can apply torque to the head of the vertical shaft,causing the variable length beam to mechanically extend or contract inoverall length.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of the variablelength beam of the present invention in a contracted state;

FIG. 2 is a perspective view of the embodiment of FIG. 1 shown in anextended state;

FIG. 2( a) is a cross-section of the embodiment of FIG. 2 along the line2(a)-2(a);

FIG. 3 is an exploded perspective view of the variable length beam ofFIGS. 1 and 2;

FIG. 3( a) is an exploded perspective view of a second embodiment of thevariable length beam of the present invention;

FIG. 4 is an enlarged view of the screw drive shown in FIG. 3( a);

FIG. 5 is a top view, partly in phantom, of the variable length beam ofFIGS. 1 and 3, shown closed, with a breakaway piece at the far right,which represents any of the aforementioned fixed beam components;

FIG. 6 is a cross-section of the variable length beam of FIGS. 1, 3, and5 along the line 6-6 of FIG. 5;

FIG. 7 is a top view, partly in phantom, of the second embodiment of thevariable length beam of the present invention as shown in FIG. 3( a);

FIG. 8 is a cross-section of the variable length beam of FIGS. 3( a) and7 along the line 8-8 of FIG. 7;

FIG. 9 is a bottom perspective view of two panels placed on either sideof a diaphragm of a bridge in construction showing use of the variablelength beam of the present invention, with the area over the diaphragmconstructed with fill-in stringers and decking;

FIG. 10 is a perspective view, partially broken away, of an assembledbridge panel, showing use of the variable length beam of the presentinvention;

FIG. 11 is a perspective view of multiple adjustable panels, with DetailA, a blow-up, illustrating the use of the variable length beam of thepresent invention in such adjustable panels; and

FIG. 12 is a side elevation of an adjustable panel suspended fromhangers, showing the use of the variable length beam of the presentinvention in such adjustable panels.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a variable length beam which is useful inbridge construction, especially in adjusting the dimensions of falseworksupport beams used in cast-in-place bridge deck forming. Although thevariable length beams of this invention could be used by themselves assupport members in any number of load transfer configurations, theirmost advantageous use is in combination with fixed length components tocreate joists which support a system of parallel stringers in panels ofvarying widths. For example, a variable length beam comprised of twomodified 1′-6″ components can be used with one or more standard lengthcomponents of 1′-6″, 3′-0″, 6′-0″, or 12′-0″ to provide beam lengthswhich are not otherwise readily available. Some of the advantages ofsuch use are as follows:

-   -   eliminating the waste of dimensional lumber (ultimately        discarded and replaced) used as transverse joist members which        are cut to fit the variable bay width experienced from one        bridge to another;    -   providing a reusable, panelized form system, that is easily        configurable to varying bridge girder spans and bay widths;    -   reducing the time allocated to deck forming and stripping on a        job-site by allowing the majority of the forming to be completed        off-site, and eliminating the need to disassemble the form        system when stripping from the completed cast-in-place concrete        deck;    -   increasing the level of worker safety by minimizing the time        spent elevated and tied off on the structural bridge beams;    -   reducing the overall cost of constructing cast-in-place concrete        bridge decks by decreasing the time expended to form and strip        the deck falsework system; and    -   decreasing the impact of construction upon the traveling public        by requiring less construction time and bringing the new bridge        on-line more quickly.

The invention will be better understood by reference to the drawings, inwhich similar parts are indicated by use of the same reference numeralin each of the figures in which that part is depicted.

Referring now to FIG. 1, the numeral 10 represents a first embodiment ofthe variable length beam of the present invention having side channels12 which are provided with end-plates 14. Travel support beams 16, whichhave stop tabs 15, are fitted within side channels 12, which receivestructural bolts 18 for positioning with respect to travel support beams16. Side stiffeners 20 are connected to side channels 12 to strengthenvariable length beam 10. Central stiffener assembly 22 and two modifiedend-plates 24 are provided midway between the end-plates 14

FIG. 2 depicts variable length beam 10 in an extended state. In additionto the elements shown in FIG. 1, slots 26 are shown in the tops oftravel support beams 16 for accommodating structural bolts 18. Slots arealso present in the bottom flanges of travel support beams 16 (notshown).

From FIG. 2( a), a cross-section of the extended variable length beam 10of FIG. 2, it can be seen that travel support beams 16 are fitted withinside channels 12. Nuts 19 fix the position of structural bolts 18 withinslots 26 (shown in FIG. 2), thereby controlling the position of sidechannels 12 relative to travel support beams 16 and adjusting the lengthof variable length beam 10.

The elements making up the variable length beam of FIGS. 1 and 2 areshown prior to final assembly in FIG. 3. Central stiffener assembly 22and modified end-plates 24 enable manually moving a pair of sidechannels 12 along a pair of travel support beams 16 to extend orcontract the variable length beam of the present invention.

FIG. 3( a) illustrates a preferred embodiment of the variable lengthbeam of the present invention, previously referred to as the secondembodiment, in which extension or contraction of the variable lengthbeam is accomplished mechanically by means of a screw drive mechanism30, more particularly shown in FIG. 4, rather than manually. Modifiedend plates 27 and 28, which are threaded, cooperate with screw drivemechanism 30 to enable mechanically moving a pair of side channels 12along a pair of travel support beams 16. Modified end-plate 28 has astandard or clockwise thread whereas modified end-plate 27 has a reverseor counterclockwise thread. Screw drive 32 has a clockwise thread tocooperate with the clockwise thread of modified end-plate 28, whilescrew drive 34 has a counterclockwise thread to cooperate with thecounterclockwise thread of modified end-plate 27. Screw drive 32 hasaffixed to it a shaft keeper 36 and a first bevel gear 38, which isaligned tangentially to a second bevel gear 40 affixed to a verticalshaft 42, which is mounted within a central stiffener assembly 22, whichserves as a gear housing. Application of torque to the head of shaft 42will cause bevel gears 40 and 38 to rotate standard thread screw drive32 and reverse thread screw drive 34 within modified end-plates 28 and27, respectively, moving side channels 12 along travel support beams 16to extend or contract the variable length beam of the present invention.

FIGS. 5 and 6 show additional details of the first embodiment of thevariable length beam of the present invention as illustrated in FIGS. 1and 3, including attachment of a fixed beam component.

FIGS. 7 and 8 show additional details of a preferred embodiment of thevariable length beam of the present invention as illustrated in FIGS. 3(a) and 4, including attachment of a fixed beam component.

FIG. 9 shows how the variable length beams of the present invention areused in bridge deck forming. Hanger assemblies 74 support a plurality ofjoists 56 comprised of variable length beams 10 and fixed lengthcomponents 76, which in turn support a plurality of stringers 54, uponwhich plywood decking 62 is laid to serve as a base for concrete, whichis poured upon plywood decking 62. The fill-in area over a diaphragm 50attached to bridge beams 70 is shown at area 58.

FIG. 10 shows use of the variable length beams of the present inventionin a preassembled deck panel 60 which comprises a series of joists 56utilizing variable length beams 10 as a part thereof, which joistssupport a series of stringers 54, which in turn support plywood decking62.

FIG. 11 shows a series of adjustable panels 60 between bridge girders70. The fill-in area 58 occurs at the location of each permanentdiaphragm 50. Detail A shows plywood decking 62 laid upon a series ofstringers 54, which are supported by a series of joists 56 (one shown).The joists are comprised of variable length beams 10 and a fixedcomponent.

In FIG. 12 diaphragm 50 is shown between two bridge girders 70supporting hanger assemblies 74, which support joists 56, parts of whichare comprised of variable length beams 10. A series of stringers 54 aresupported by joists 56 and support plywood decking 62, which supports areinforced concrete deck 72.

By creating variable length beams which can be used in joists toconstruct adjustable panels for supporting bridge decking, a reusabledeckwork forming system is provided.

It will be appreciated that the disclosure and description in theinstant specification are set forth by way of illustration and notlimitation, and that various modifications and changes may be madewithout departing from the spirit and scope of the present invention.

1. In a bridge decking panel comprising a plurality of joists supportinga plurality of stringers, which support a plywood decking, theimprovement wherein said bridge decking panel is removable and reusablein its entirety and each of said joists contains a variable length beamcomprising twin parallel travel support beams connected to one another,said twin parallel travel support beams supporting two beam componentsmovable longitudinally with respect to one another along said twinparallel travel support beams, to lengthen or shorten said variablelength beam.
 2. The bridge decking panel of claim 1, wherein said twinparallel travel support beams of said variable length beam are connectedto one another at their midpoints through a central stiffener assembly.3. The bridge decking panel of claim 2, wherein said twin paralleltravel support beams of said variable length beam have stop means ateach end thereof.
 4. The bridge decking panel of claim 3, wherein saidtwo beam components of said variable length beam are modified beamcomponents adapted for longitudinal movement upon said twin paralleltravel support beams.
 5. The bridge decking panel of claim 4, whereineach of said two beam components of said variable length beam has a pairof oppositely facing side channels which contain said twin paralleltravel support beams.
 6. The bridge decking panel of claim 5, whereinone end of each pair of said side channels of said variable length beamis closed by an end-plate.
 7. The bridge decking panel of claim 6,wherein the opposite end of each pair of said side channels of saidvariable length beam is open, and wherein modified end-plates close thelateral space between each pair of side channels at said opposite endthereof.
 8. The bridge decking panel of claim 7, wherein a sidestiffener is attached to each of said side channels of said variablelength beam.
 9. The bridge decking panel of claim 8, wherein said twinparallel travel support beams of said variable length beam have stoptabs at each end thereof, said stop tabs being adapted to interact withsaid side stiffeners upon extension of said variable length beam to apredetermined maximum length.
 10. The bridge decking panel of claim 9,wherein said central stiffener assembly of said variable length beamcontains a horizontally mounted screw drive having a clockwise thread atthe proximal end thereof and a counterclockwise thread at the distal endthereof, said proximal end of said screw drive being supported by amodified end-plate having a clockwise-threaded receiving plate and saiddistal end of said screw drive being supported by a modified end-platehaving a counterclockwise-threaded receiving plate, said screw drivehaving a shaft keeper and a first bevel gear attached thereto, saidfirst bevel gear meshing tangentially with a second bevel gear attachedto a vertically mounted shaft. 11-13. (canceled)
 14. A reusable,variable width bridge decking panel comprising a plurality of joistssupporting a plurality of stringers, which support a plywood decking,said bridge decking panel being removable and reusable in its entirety,each of said plurality of joists being of variable length.
 15. Thebridge decking panel of claim 14, wherein each of said plurality ofjoists contains a variable length beam comprising twin parallel travelsupport beams connected to one another, said twin parallel travelsupport beams supporting two beam components movable longitudinally withrespect to one another along said twin parallel travel support beams, tolengthen or shorten said plurality of joists.
 16. A variable length beamcomprising twin parallel travel support beams connected to one another,said twin parallel travel support beams supporting two beam componentsmovable longitudinally with respect to one another along said twinparallel travel support beams, to lengthen or shorten said variablelength beam.